[PATCH v2 3/3] tpm: in tpm2_del_space check if ops pointer is still valid

[Lino Sanfilippo]

From: Lino Sanfilippo <l.sanfili...@kunbus.com>

In tpm2_del_space() the sessions are flushed by means of the tpm_chip
operations. However the concerning operations pointer my already be NULL at
this time in case that the chip has been unregistered (see
tpm_chip_unregister() which calls tpm_del_char_device() which sets
chip->ops to NULL).
Before accessing chip->ops check if it is still valid. Skip flushing
the sessions in this case.

Signed-off-by: Lino Sanfilippo <l.sanfili...@kunbus.com>
---
 drivers/char/tpm/tpm2-space.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 784b8b3..9a29a40 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -58,12 +58,17 @@ int tpm2_init_space(struct tpm_space *space, unsigned int 
buf_size)
 
 void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space)
 {
-       mutex_lock(&chip->tpm_mutex);
-       if (!tpm_chip_start(chip)) {
-               tpm2_flush_sessions(chip, space);
-               tpm_chip_stop(chip);
+       down_read(&chip->ops_sem);
+       if (chip->ops) {
+               mutex_lock(&chip->tpm_mutex);
+               if (!tpm_chip_start(chip)) {
+                       tpm2_flush_sessions(chip, space);
+                       tpm_chip_stop(chip);
+               }
+               mutex_unlock(&chip->tpm_mutex);
        }
-       mutex_unlock(&chip->tpm_mutex);
+       up_read(&chip->ops_sem);
+
        kfree(space->context_buf);
        kfree(space->session_buf);
 }
-- 
2.7.4